NetBSD Problem Report #54992

From ryo@moveq.nerv.org  Thu Feb 20 21:04:14 2020
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Date: Fri, 21 Feb 2020 04:14:10 +0900 (JST)
From: ryo@nerv.org
Reply-To: ryo@nerv.org
To: gnats-bugs@NetBSD.org
Subject: hosts_access(5) doesn't work for IPv6 linklocal address without scope-id
X-Send-Pr-Version: 3.95

>Number:         54992
>Category:       lib
>Synopsis:       hosts_access(5) doesn't work for IPv6 linklocal address without scope-id
>Confidential:   no
>Severity:       non-critical
>Priority:       medium
>Responsible:    ryo
>State:          closed
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Thu Feb 20 21:05:00 +0000 2020
>Closed-Date:    Mon Mar 30 08:37:51 +0000 2020
>Last-Modified:  Mon Mar 30 08:37:51 +0000 2020
>Originator:     Ryo Shimizu
>Release:        NetBSD 9.99.46
>Organization:
>Environment:
System: NetBSD subq 9.99.46 NetBSD 9.99.46 (SUBQ) #17: Mon Feb 10 02:58:24 JST 2020 ryo@subq:/usr/src/sys/arch/amd64/compile/SUBQ amd64
Architecture: x86_64
Machine: amd64
>Description:

  [hosts.allow]
  ALL: [fe80::%re0/16]	# this works

but,

  [hosts.allow]
  ALL: [fe80::/16]	# this doesn't work.


>How-To-Repeat:

  hostA# echo 'ALL: [fe80::/16]' >> /etc/hosts.allow
  hostB# ssh fe80::6d9:f5ff:fe06:e273%wm2

connect to linklocal address of hostA, but connection refused.


>Fix:

In this case, it should be compared only addresses, with or without scope-id.

libwrap/hosts_access.c:masked_match6() always compares scope_id when the address is linklocal.
(e.g., string="fe80::1efd:8ff:fe70:5d2e%re0", net="fe80::", mask="16")

>    if (addr.sa.sa_family == AF_INET6 && addr.sin6.sin6_scope_id &&
>        addr.sin6.sin6_scope_id != net.sin6.sin6_scope_id)
>	return NO;

'addr' is a client address extracted by getaddrinfo() from 'string' argument,
and 'net' is address/mask written in /etc/hosts.{allow,deny}.

when addr is a linklocal, the 2nd condition (addr.sin6.sin6_scope_id) is true, but
'net' may not have valid scope-id, therefore

    if (addr.sa.sa_family == AF_INET6 && addr.sin6.sin6_scope_id && net.sin6.sin6_scope_id &&
        addr.sin6.sin6_scope_id != net.sin6.sin6_scope_id)
	return NO;

However, this is too verbose, so the following is sufficient.

Index: hosts_access.c
===================================================================
RCS file: /src/cvs/cvsroot-netbsd/src/lib/libwrap/hosts_access.c,v
retrieving revision 1.21
diff -a -u -r1.21 hosts_access.c
--- hosts_access.c	17 Feb 2016 19:52:20 -0000	1.21
+++ hosts_access.c	19 Feb 2020 18:01:24 -0000
@@ -561,7 +561,7 @@
     for (i = 0; i < alen; i++)
 	ap[i] &= mp[i];

-    if (addr.sa.sa_family == AF_INET6 && addr.sin6.sin6_scope_id &&
+    if (addr.sa.sa_family == AF_INET6 && net.sin6.sin6_scope_id &&
         addr.sin6.sin6_scope_id != net.sin6.sin6_scope_id)
 	return NO;
     return (memcmp(ap, np, alen) == 0);

>Release-Note:

>Audit-Trail:
From: "Ryo Shimizu" <ryo@netbsd.org>
To: gnats-bugs@gnats.NetBSD.org
Cc: 
Subject: PR/54992 CVS commit: src/lib/libwrap
Date: Mon, 30 Mar 2020 08:34:39 +0000

 Module Name:	src
 Committed By:	ryo
 Date:		Mon Mar 30 08:34:38 UTC 2020

 Modified Files:
 	src/lib/libwrap: hosts_access.c

 Log Message:
 PR/54992: fix hosts_access(5) to works for IPv6 linklocal address without scope-id


 To generate a diff of this commit:
 cvs rdiff -u -r1.21 -r1.22 src/lib/libwrap/hosts_access.c

 Please note that diffs are not public domain; they are subject to the
 copyright notices on the relevant files.

Responsible-Changed-From-To: lib-bug-people->ryo
Responsible-Changed-By: ryo@NetBSD.org
Responsible-Changed-When: Mon, 30 Mar 2020 08:37:51 +0000
Responsible-Changed-Why:
mime


State-Changed-From-To: open->closed
State-Changed-By: ryo@NetBSD.org
State-Changed-When: Mon, 30 Mar 2020 08:37:51 +0000
State-Changed-Why:
fixed


>Unformatted:

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